Spark

DTC P0504 or P0571

The brake lamp switch signal circuit and the redundant brake switch signal circuit are direct hardwire inputs to the engine control module (ECM) from the brake switch assembly. The engine control module (ECM) monitors the brake lamp switch signal circuit and the redundant brake switch signal circuit. The brake lamp switch is normally open while the redundant brake switch is normally closed. The ECM monitors the status of the brake lamp switch signal circuit and the redundant brake switch signal circuit to see if they match when the brake pedal is pressed or released.

P0504

P0571

P0504

The ECM detects that the states of the two brake switches does not match for greater than 2s when changing the states.

P0571

The ECM detects that the brake lamp is not ON and the brake lamp transition is not occurred for 3s while the vehicle is stopped.

DTC P0504 and P0571 are Type C DTCs.

DTC P0504 and P0571 are Type C DTCs.

Schematic Reference

Engine Controls Schematics : Siemens ECM - LPG with LCP → Siemens ECM - Gas without FX3 or LCP → Delphi ECM - FX3

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the scan tool brake pedal position parameter and redundant brake switch parameter while depressing the brake pedal. The readings should change between Applied and Released.
2. Operate the vehicle within the Conditions for Running the DTC, to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

1. Ignition OFF, disconnect the harness connector at the B103 brake lamp switch.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal below and ground.

•	Ignition circuit terminal 1 of the B103 brake lamp switch and ground

•	Ignition circuit terminal 4 of the B103 brake lamp switch and ground

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.

3. Verify the scan tool brake pedal position parameter is Released and the redundant brake switch parameter is Applied.

⇒	If not the specified value, test the signal circuit terminals 2 and 3 for a short circuit to voltage. If the circuits test normal, replace the B103 brake lamp switch.

4. Install a 3A fused jumper wire between the signal circuit terminal 2 and the ignition circuit terminal 4. Verify the scan tool brake pedal position parameter is Applied.

⇒	If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the B103 brake lamp switch.

5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the ignition circuit terminal 1. Verify the scan tool redundant brake switch parameter is Released.

⇒	If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the B103 brake lamp switch.

6. If all circuits test normal, test or replace the B103 brake lamp switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.